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Topic Review (Newest First)

08-28-2012 08:06 AM

dave350v8

Quote:

Originally Posted by JeffB

You may want to look at swapping to this cam:Lunati 60104 - Lunati Voodoo Camshafts - Overview - SummitRacing.com you have the springs to handle the additional lift,this cam is designed to bring back some of the low and mid-range you lost with the 210cc heads please read the description at the bottom of the specs,as mentioned earlier do advance the cam 4 degrees,some rear gears in the 3:70's will be a big help too.

That looks a good cam! Think it might be worth doing, thanks for your input!
When I build my next engine I will know a lot more for sure!

08-27-2012 05:40 PM

JeffB

You may want to look at swapping to this cam:Lunati 60104 - Lunati Voodoo Camshafts - Overview - SummitRacing.com you have the springs to handle the additional lift,this cam is designed to bring back some of the low and mid-range you lost with the 210cc heads please read the description at the bottom of the specs,as mentioned earlier do advance the cam 4 degrees,some rear gears in the 3:70's will be a big help too.

08-27-2012 05:28 PM

engineczar

Quote:

Originally Posted by machine shop tom

Along with the loss of compression from going from a 60ish cc chamber to 64ccs, you have also lost perhaps a point of effective compression because you went from a cast iron head to aluminum head. If you want to stick with flat-tops, you would be better served with a cast-iron head, perhaps an EngineQuest Vor-Tec head with the manifold mating surface that matches your existing intake manifold.

tom

Not to hijack the thread but I just used a set of those on an inboard boat engine. I have to say I was pretty impressed with them. The quality of the castings was up there and even the valve job could have been used right out of the box. For my customer it was a win win because he was able to retain his cast iron intake and get the benefit of a vortec style chamber. The price was also a steal at $280 each bare.

08-27-2012 05:00 PM

machine shop tom

Along with the loss of compression from going from a 60ish cc chamber to 64ccs, you have also lost perhaps a point of effective compression because you went from a cast iron head to aluminum head. If you want to stick with flat-tops, you would be better served with a cast-iron head, perhaps an EngineQuest Vor-Tec head with the manifold mating surface that matches your existing intake manifold.

tom

08-27-2012 04:52 PM

dave350v8

Quote:

Originally Posted by oldbogie

Certainly a bigger carb say around 750 CFM on an Edlebrock Performer RPM intake with long tube headers of 1-3/4 or 1-7/8ths tubes combining Skip's deep breather heads with this cam, the engine ought to go to over 400 horses I guess somewhere from 5800 to 6200 RPMs. It's likely to be peaky; it also may take 1.6 rockers to get there.

This whole thing, and this includes the performance from your older camel humps, really gets the engine into an area where in a systems integration sense, sum of the parts and the tune, it can gain or lose gobs of power on incredibly small often seemingly innocuous changes/exceptions/deviations of things. So with a change, as the one you did with the heads, can make it difficult to dial it back in. You just have to mess with it and that could include as was suggested advancing the cam a few degrees, I havent used a Skip White cam so I don't know if he grinds them straight up or advances them as Comp and others do. So you've got to be a bit thoughtful here. Comps come with about 4 degrees already in them so sometimes adding more isn't helpful. I just don't know if Skip's cams are the same way of not. Like Jim Miller, he touches base in here sometimes maybe you'll hear from him about this.

Your cam numbers tell you that the valve closed to closed timing is 280 degees, SAE (Society of Automotive Engineers here in the U.S.) specify this measure at .006 inch lift, whether that is really done here I don't know. 230 degrees is the duration measure from the point where the valve opened to .050 inch and is .050 inch from being closed. The difference between these two points is mostly ramps to ease the lifter and valve train motion into opening smoothly without flexing the pushrod and sitting the valve down without bouncing it. The .480/.510 inch measure would be the amount of intake and exhaust opening, respectivly, over the peak of their lobes. This is valve opening not lift at the lobe, there is a rocker between these two places. For the Chevy Small Block this is usually given for a 1.5 to 1 rocker ratio. So the actual lift happening at the lobe would be 50 percent less or .320/.340 inch. A 1.6 to 1 rocker would add 1.067 to the 1.5 rocker ratio and lift so that lift at the valve would go to .512/.544 inch with this cam.

Stiffer gears would improve acceleration performance by increasing the mechanical advantage the engine has over the mass it needs to move. Plus, it moves the RPMs higher for any given road speed to where more engine power is available. So gearing is a double advantage in terms of power delivered between the tire and ground. The downside of stiffer gears is higher fuel consumption, noise, vibration and wear.

Bogie

Thanks Bogie for taking the time to explain these things to me! I will have to
read it several times to get it to sink in but I will get there!
The cam I have in at the moment is a compcams magnum 280 480/480 lift so
smaller than what skip white advises, and as you said this has already 4 degrees in it so I wont be advancing that!

The lightness of my car(2600lbs) should help me with the bigger port runners
then?
Thanks again

08-27-2012 04:06 PM

oldbogie

Quote:

Originally Posted by dave350v8

Hi
bogie and engineczar both of you are spot on! It does seem to at least match the camels at lower revs but then it wants to rev further than them!
The advertised duration is 280 and at .50 intake/exhaust is 230 degrees.
To be honest I dont fully understand these figures.

Skip whites website states with a cam around 480/510 lift it dynos at just over 400 horsepower on a 350.

Do you think changing rear gears and a bigger carb will help, I was considering a cam change as well if you have any suggestions?
Thanks again

Certainly a bigger carb say around 750 CFM on an Edlebrock Performer RPM intake with long tube headers of 1-3/4 or 1-7/8ths tubes combining Skip's deep breather heads with this cam, the engine ought to go to over 400 horses I guess somewhere from 5800 to 6200 RPMs. It's likely to be peaky; it also may take 1.6 rockers to get there.

This whole thing, and this includes the performance from your older camel humps, really gets the engine into an area where in a systems integration sense, sum of the parts and the tune, it can gain or lose gobs of power on incredibly small often seemingly innocuous changes/exceptions/deviations of things. So with a change, as the one you did with the heads, can make it difficult to dial it back in. You just have to mess with it and that could include as was suggested advancing the cam a few degrees, I havent used a Skip White cam so I don't know if he grinds them straight up or advances them as Comp and others do. So you've got to be a bit thoughtful here. Comps come with about 4 degrees already in them so sometimes adding more isn't helpful. I just don't know if Skip's cams are the same way of not. Like Jim Miller, he touches base in here sometimes maybe you'll hear from him about this.

Your cam numbers tell you that the valve closed to closed timing is 280 degees, SAE (Society of Automotive Engineers here in the U.S.) specify this measure at .006 inch lift, whether that is really done here I don't know. 230 degrees is the duration measure from the point where the valve opened to .050 inch and is .050 inch from being closed. The difference between these two points is mostly ramps to ease the lifter and valve train motion into opening smoothly without flexing the pushrod and sitting the valve down without bouncing it. The .480/.510 inch measure would be the amount of intake and exhaust opening, respectivly, over the peak of their lobes. This is valve opening not lift at the lobe, there is a rocker between these two places. For the Chevy Small Block this is usually given for a 1.5 to 1 rocker ratio. So the actual lift happening at the lobe would be 50 percent less or .320/.340 inch. A 1.6 to 1 rocker would add 1.067 to the 1.5 rocker ratio and lift so that lift at the valve would go to .512/.544 inch with this cam.

Stiffer gears would improve acceleration performance by increasing the mechanical advantage the engine has over the mass it needs to move. Plus, it moves the RPMs higher for any given road speed to where more engine power is available. So gearing is a double advantage in terms of power delivered between the tire and ground. The downside of stiffer gears is higher fuel consumption, noise, vibration and wear.

Bogie

08-27-2012 03:59 PM

dave350v8

Quote:

Originally Posted by ap72

As it sits, HEADERS AND EXHAUST should be on the top of your priority list. I realize they may not make headers for your car, but custom ones can be made by you or a shop. You can get a kit with flanges and bends to get you started. Through in some good merge collectors and dual 3" exhaust and you'll see some serious power increase.

Just remember air can only come in as fast as it goes out. Also, a strong clean exhaust pulse can really draw in a lot of extra air through the intake.

There's a lot of things you can do to your car to get you some power but your engine is already being choked by the exhaust.

Thanks for that,will have a go at making my own headers then, im going to
change carb and advance cam, do you think I will get near 400 horsepower?

08-27-2012 03:34 PM

ap72

As it sits, HEADERS AND EXHAUST should be on the top of your priority list. I realize they may not make headers for your car, but custom ones can be made by you or a shop. You can get a kit with flanges and bends to get you started. Through in some good merge collectors and dual 3" exhaust and you'll see some serious power increase.

Just remember air can only come in as fast as it goes out. Also, a strong clean exhaust pulse can really draw in a lot of extra air through the intake.

There's a lot of things you can do to your car to get you some power but your engine is already being choked by the exhaust.

08-27-2012 03:05 PM

vinniekq2

advance what you have to see the behavior then bogie will give ya the works

08-27-2012 02:42 PM

dave350v8

Will try advancing cam then! Will do carb first as this is 30 minutes to do!
Would I gain more by putting in a bigger lift cam though?
thanks

08-27-2012 02:33 PM

vinniekq2

advancing your cam will make more cylinder pressure so more bottom end,generally,it robs from the top end though.This will tell old bogie what is happening and he will give 2 pages of ideas later. do 1 thing at a time.change the carb first and see what happens then cam or the other way around

08-27-2012 02:25 PM

dave350v8

Yes I see what you mean! What does advancing the cam do as you have suggested?
Would a bigger carb help now,I have a 650dp on the shelf and a 750v/s

Yes my tyres are 23 inches in diameter! do you think that will be ok with the T5 ratios
and 3.9 rear?
I doubt I am anywhere near 400 horsepower now!

Thanks again

08-27-2012 02:05 PM

vinniekq2

a 2600 pound car with 400 hp should run low 12s or better.the tires are only 23 inches? I think the heads are too big for a stock 350.If you are fast with a wrench the full the front off and advance the cam 4 degrees,couple hours and gaskets. If that perks it up then what bogie said about reversion,,,
NOTE:the top end increase in HP,you might not feel by seat of your pants driving even if you got 25 more horses.
If advancing the cam changes things a lot,then retuning is in order,probably cam and intake.

what you have done is put on entry level race heads on a very mild street engine. Think of it like putting an 850 double pumper on a stock 283

08-27-2012 01:18 PM

dave350v8

Quote:

Originally Posted by oldbogie

Could help, the T5 has ratios all over the place as well, do you know what these are? A 3.09 matched with a 700R4 or 4L60 comes out of the hole pretty hard but that is the combination of 3.53 low and the torque-multiplication of the converter, certainly the latter is something you don't get with a clutch.

Bogie

Hi, the trans gears are 1st 2.95:1 2nd 1.94:1 3rd 1.34:1 4th 1:1

My rear gears are 3.09 and tyre diameter is 23 inches if that helps

My car weighs 2600 lbs
Realistically what horsepower do you think I might have? What should I expect down the strip?
Sorry for all the questions!

08-27-2012 01:01 PM

oldbogie

Quote:

Originally Posted by dave350v8

Hi
bogie and engineczar both of you are spot on! It does seem to at least match the camels at lower revs but then it wants to rev further than them!
The advertised duration is 280 and at .50 intake/exhaust is 230 degrees.
To be honest I dont fully understand these figures.

Skip whites website states with a cam around 480/510 lift it dynos at just over 400 horsepower on a 350.

Do you think changing rear gears and a bigger carb will help, I was considering a cam change as well if you have any suggestions?
Thanks again

Could help, the T5 has ratios all over the place as well, do you know what these are? A 3.09 matched with a 700R4 or 4L60 comes out of the hole pretty hard but that is the combination of 3.53 low and the torque-multiplication of the converter, certainly the latter is something you don't get with a clutch.

Bogie

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